Osborne has described the behaviour as going against the "spirit of the law". But in a heated parliamentary debate on the issue yesterday, business minister Margot James said 90 per cent of M&S employees will get a higher pay as a result of the changes.

"I make no apology for trying to set the record straight when I feel that a company, or perhaps an individual, in the outside world has been maligned unfairly," she said.

Conservative MP James Berry cautioned against introducing any more legislation on wages, saying he worried businesses would become "wrapped up" in layers of regulation.

"I hope this government will continue to criticise employers who do not follow the spirit of the rule, so that we as customers can also take direct action by not shopping at M&S this Christmas if we are not happy about how they treat their staff," Berry said.

A spokesperson for Marks & Spencer said: “Over 99 per cent of colleagues have agreed to pay and pension changes which will reward our people in a fair and consistent way, simplify and modernise our business and make our colleagues amongst the highest paid in UK retail. The vast majority will receive higher total pay as a result of the pay changes and nobody need be worse off.”